Heat interchanger



W. B. CROAN HEAT INTERGHANGER Filed April 21. 1924 Wzcz l Maxim.

Patented Oct. 18, 1927.

" UNITED STATES WALTER CROAN, F CHICAGO, ILLDN'OIS.

HEAT INTERCHANGEB.

Application led yApril 21, 1924. Serial No. 707,971.

The main object of this invention is to produce an improved heat interchanger for universal use and of economical construction; to provide a radiator capable of operating on direct steam pressures obtained from power boilers, thus permitting the use of direct high temperature steam for indirect radiation-and at the saine time to provide a highly efficient and reliable heat interl" changing device adapted for use in vacuum,

hot water, low pressure steam, and other systems; to provide an improved radiator which is applicable for both direct and indirect systems.

Radiators placed in a room are termed direct radiators. In such radiators the temperature is seldom above the boiling point of water, and the pressures correspond with the temperatures. Indirect radiation is used n where ventilation as well as heating is required, and the range of temperature is controlled largely by the range of pressure available. One of the main uses of indirect radiators is in connection with the `blower system of heating. Indirect radiation is also used where the temperature of the air to be delivered by the radiator, as used in drying systems, ranges from 200 to 400 degrees 1 Fahrenheit. v

'o The heat transmission of a direct radiator is usually expressed in terms of a transmission constant, or the B. t. u. emitted per hour per square foot of external surface per degree in temperature between the heating medium and the surrounding air. For direct radiationthe value of this constant varies from substantially 1.5 for cast iron radiators and goes to approximately 2.18 for wall type radiators and for pipe coils.

The main object of this invention is the production of a light cast iron radiator, which is especially adapted for indirect radiation and where the required delivery temperature of the air necessitates the useof steam under pressures from 5() to 125 pounds gage. Such indirect radiators are operated in a duct with the blower system, so that air rapidly passing such a radiator must be able to make a rapid interchange of heat. The principal and main points in the construction of such a radiator are: First, it must have the mechanical strength to stand the high pressures. Second, it must have a large radiating surface, such radiating surface so disposed as to promote the rapid transmission of heat through the iron and fromthe steam or other heating medium to the air or other uid passing the coils. The third and one of the most important items 1n the construction of a radiator for indirect radiation is that when placed in an enclosed passage it is an obstruction to the current oi' air. It becomes very necessary that such an obstruction should not disturb the even distribution of velocity throughout the conduit, and mechanically should form tle least possible obstruction to the passage o air.

The even distribution of pressure and velocity in a conduit is through this invention accomplished by designing the radiator with a v ery large number of air or fluid passages which are symmetrically arranged over the entire surface, each individual passage being substantially a Venturi tube.

An important property of the Venturi tube form for the air passages is that it increases the pressure of the air on the heating surfaces as it passes through the radiator. The increased pressure of the air forces the air into more intimate contact with the surface of the tube so that the passage of air through the tube substantially wipes the exposed iron surface of the radiator, thus more effectively taking up the heat.

The obstruction to the flow of air is very slight because of the stream-line sectional Jform of the tins and steam conduits and the fact that these structures are placed edgewise to the flow. The entire radiating surface is of Venturi tube form, and further, all of the metal comprising the radiating surfaces or iins is disposed in such a manner as to reinforce the steam carrying conduit giving a high factor of safety.

Referring to the drawings,-

Figure 1 is a front elevation partly in section of a specific form of radiator embodying this invention.

Fig. 2 is an end view partly in section along the line 2-2 of Fig. 1. p

Fig. 3 is a section view along the line 3-3 of Fig. 1.

Fig. 4 is a section view along the line H of Fig. l.

In the form shown, the radiator comprises headers 1 and steam conduits 2, and reinforcing :fins 3. The ends of the headers are provided with tapped openings 4. The preferred sectional form of the steam conduits 5 is shown as in Figs. 3 and 4. The transverse sectional form of the lins is shown in Fig. 2.

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The arrangement and shapes of the'n and the conduit surfaces forms between them a multiplicity of Venturi tubes.

The radiator is a single casting in which the fins 3 act as reinforcement for the steam conduits 2.

This design is of special interest in foundry production processes, since it makes an ideal attern to be 'drawn out of the sand and provi es a symmetrical arrangement of the cores of Vthe steam passages. This desi alsoV provides for the maximum strengt due in part to the fact that the metal is s o distributed that in the casting process, uniform cooling takes place throughout the casting thus preventing strains due to uneven shrinkage and crystallization. This construction also makes possible headers cast inteal withthe steam conduits and entirely evoid of joints of any kind.

In installing this type of radiator, all that is necessary is to connect it with the inlet and outlet pipes.

It has an extraordinarily high heat transmission coeiiicient. Tests of the radiator when used for direct radiation show that its constant is above 2 and when used with high pressure steam for delivery of high temperature air for indirect heating purposes, the contact is very much above that of `pipe coils even when equipped with fins.

The form of the radiator is also advantageous, being smooth and even throughout and substantially rectangular in outline. There is no special back or front or top or bottom. It Works and drains properly in any ositon since the openings are symmetrical y disposed at the four corners thereby preventing the formation of. a trap in the circulation system. When drained the amount of water left in the ockets in this radiator, independent of position, is so small that it is of no importance. When 'designed with closely spaced steam 'ducts and fins as illustrated, the radiator becomes a reinforced grill or grating which can be installed floor ush and used to fill an aperture in the floor or in a walk.

In indirect heating systems where radiators are installed in a. duct, it is often necessary to connect the radiators to a high pres# sure steam line, necessitating the use of pressure regulators and steam traps and a special return steam pipe line back to the source ofsupply. Such construction is neoeary because ordinary radiators are not capable of withstanding the steam pressures used for power purposes and their installation rethe extra expense of the installation of t e re maintenance and in erent losses in the regulators, cost of the traps and their installaf tion, the cost of the special return pipe and umps which are required to return the conensed steam. It also becomes necessary in order to secure high temperatures with low pressure steam to stack thc radiators which requires not onl the expense of installin extra radiators, but the installation of suc extra radiators in a duct means increased air resistance and therefore increased force or blower ca acity. This increases both the cost of instal ation and operating expense.

.The herein described high pressure radlators, can be connected direct to the high pressure steam line whereby the radiators operate at a hi her temperature, a smaller number of radiators" will be required, the steam line will be of smaller capacity, and no extra return or traps or umps will be required, since the condensed steam can return by gravity.

Although but one specific embodiment of this lnvention has been herein shown and descrlbed, 1t will be understood that numerous details of the construction shown may be altered' or omitted without de arting from the splrit of this invention as efined by the following claims.

I claim:

1. A steam radiator comprising a pair of separate spaced headers, a plurality of indepen'dent lmperforate tubes of elongate cross sectlon arran d with the major axes of the elongate sections extending from front to back of the radiator, said tubes being connected at their ends to said headers so as to provlde communication between said headers, and a lplurality of solid radiating fins inegbll wit and 'disposed transversely to said 2. A steam radiator comprisin a air of separate spaced headers, a plurality o independent imperforate tubes of diamond shaped cross section arranged with the ma- ]or axes of the diamond shaped sections extendin from front to back ofthe radiator, said tu being connected at their ends to said headers so as to provide communication betweenv said headers, and a plurality of solid radiating fins of diamond shapedcross section lintegral with and disposed transversely to sald tubes.

Signed at Chicago this 18th day of April.

WALTER B. CROAN.

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